This invention relates to a magnetron having an anode with a plurality of vanes interconnected by ring straps.
Magnetrons are generally provided with a cylindrical anode having a plurality of radial vanes extending in an inward direction. These vanes create spaces within anode which function as multi resonating cavities. A cathode is positioned along the axis of the anode and an interaction space is formed between free edges of the vanes and the cathode. Double straps are connected between the top and bottom edges of alternate vanes in the anode to enhance operation of the magnetron. These straps are located in notches on the top and bottom edges of the vanes.
In operation, an elcetric field is formed between the anode and the cathode and a magnetic field is formed along the axis of the anode through the interaction space. Electrons from the cathode are bunched together in a spoke-like shape around the interaction space to induce microwave energy in the cavities between the anode vanes. The vanes capture electrons and, as a result, heat is generated at the free edges of the vanes. About 40% of the power of the magnetron is lost in heat a t the anode vanes.
As shown in the conventional magnetron in FIG. 5, the vanes 1 are connected to the cylindrical anode 12. When the vanes 1 are heated during operation of the magnetron, the vanes 1 expand inwardly as indicated with the arrow F.sub.1, while the straps 3 and 4 expand outwardly in the opposite direction as indicated by the arrow F.sub.2. As a result, a component force (F.sub.1+ F.sub.2) is concentrated in the corner portion 1.sub.a of the vanes 1. These vanes 1 are connected together by strap 3. Whenever the magnetron is turned on and off, a heat cycle occurs which adds force to the corner portions 1.sub.a of the vanes 1 and the strap 3. Consequently the corner portion 1.sub.a is stretched outwardly by the strap 3 resulting in either a crack 5 in the vane 1 or strap separation where the straps 3 and 4 tear off the vane 1. In either event, the magnetron stops oscillating and producing microwave energy. Vane cracks and strap separation especially occur in internal magnet type magnetrons having an anode enclosed within a magnetic cylinder, such as iron, having a lower coefficient of expansion than that of the anode and the vanes.